How to use a variable as a part of an object

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Stefan Mueller - 30 Nov 2005 20:33 GMT

To change the value of input boxes I use
document.MyForm.MyInput1.value = "Test";
document.MyForm.MyInput2.value = "Test";

Is it also possible to use a variable instead of MyInput1 and MyInput2?
I'm thinking about something like
var MyVariable = "MyInput1";
document.MyForm.MyVariable.value = "Test";

Stefan

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VK - 30 Nov 2005 20:45 GMT

> Is it also possible to use a variable instead of MyInput1 and MyInput2?
> I'm thinking about something like
> var MyVariable = "MyInput1";
> document.MyForm.MyVariable.value = "Test";

document.forms["MyForm"].elements[MyVariable].value = "Test";
// MyVariable goes without quotes of course

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RobG - 30 Nov 2005 21:00 GMT

> To change the value of input boxes I use
> document.MyForm.MyInput1.value = "Test";
[quoted text clipped - 4 lines]
> var MyVariable = "MyInput1";
> document.MyForm.MyVariable.value = "Test";

Yes:

document.MyForm.elements[MyVariable].value = "Test";

or

document.MyForm[MyVariable].value = "Test";

I prefer the former as it is clear that MyVariable refers to the form's
elements collection. Others prefer the later.

They are equivalent to:

document.MyForm.elements["MyInput1"].value = "Test";

When you use dot notation, the script engine looks for a property with
that name. When you use square brackets, the engine expects an
expression that when evaluated will give a string that can be used for
the name.

It's covered in more detail in the FAQ:

<URL: http://www.jibbering.com/faq/faq_notes/square_brackets.html >

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Rob

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Stefan Mueller - 30 Nov 2005 22:23 GMT

That's perfect.

Many thanks
Stefan

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Webmaster Forum / HTML, CSS, Scripts / JavaScript / November 2005

How to use a variable as a part of an object